It means that he can see why his brother likes you, that you are a great girl. But honestly they are brother's, he can't go behind his brother's back and go out with you, that would be betraying his brother. In this sort of case I always tend to think to myself, I may like him and he may like me, but if he is willing to betray his own brother (family always comes first), then he would have no problem in betraying me if I was his girlfriend. Who wants a guy who would betray his own brother. Just think about that. Maybe it would be better to walk away from both and find someone who's brother doesn't like you. Good Luck